1. Field of the Invention
The present invention relates to a system and method for printing an extruded sheet in which ink is directly applied to the extruded sheet with one or more print rollers.
2. Description of the Related Art
It is often desirable to enhance the appearance of plastic articles, such as vinyl siding. U.S. Pat. No. 5,662,977 describes a process for manufacturing plastic siding panels with an embossed three dimensional pattern. The embossed pattern can resemble a natural wood grain. In the process, a decorative wood grain foil is transferred to an extruded plastic sheet. The wood grain foil is formed of multiple synthetic resinous paint coats printed or cast on a temporary carrier sheet. A three dimensional wood grain texture is embossed on the surface of the laminate. Following the embossing, the foil is stripped away and the wood grain resin is transferred to the extruded plastic sheet. This patent has the drawback of using high temperatures and pressures in order for proper embossing.
Other techniques have incorporated an accent color pattern within the article. U.S. Pat. No. 5,232,751 describes a method for making a vinyl sheet article including color patterns. A colorant is mixed with a top coat compound. The compound is heated and processed so that the melted colorant spreads axially in the direction of extrusion. The color-striated compound is fused with the substrate compound.
U.S. Pat. No. 5,869,176 describes a method for extruding plastic articles having an accent color pattern. Pellets of a capstock base material such as polyvinyl chloride (PVC) are combined with accent color pellets. The accent color pellets are alloyed masses of a resin and pigment which are larger than the powder particles of the base material. During extrusion, the accent color pellets soften and disperse later than the base material to produce accent color streaks simulating wood-grain. The above described color accent techniques have the shortcoming of being difficult to control the incorporated color pattern.
It is desirable to provide a system and method for printing color or a pattern of colors on an extruded sheet which can be precisely controlled.
The present invention relates to a system and method for printing an extruded sheet in which heat curable ink is applied over the extruded sheet. The extruded sheet is at an elevated temperature. The ink cures immediately upon contact with the extruded sheet having an elevated temperature. The extruded sheet can be received against a rotating drum. The drum can include a plurality of perforations to enable a vacuum to be applied to the drum for holding the extruded sheet against the drum. Alternatively, the extruded sheet is received on a rotating belt. The rotating belt can include a plurality of perforations to enable a vacuum to be applied to the belt for holding the extruded sheet against the belt. At least one print roller is positioned adjacent the drum to apply ink on the extruded sheet. In one embodiment, at least one print roller applies a background color to the sheet and a plurality of print rollers apply one or more additional colors for forming a pattern or image on the sheet in registration with one another. For example, the pattern or image can have a wood grain appearance. The extruded sheet can be sized for use as a vinyl siding product.
The invention will be more fully described by reference to the following drawings.